NEW YORK (Reuters Health) - A growing number of Americans are being diagnosed with the painful form of arthritis known as gout -- thanks in large part, researchers say, to the national obesity epidemic.

Using data from a government health survey, researchers found that an estimated 4 percent of U.S. adults -- or 8.3 million people -- had gout in 2008. That compares with just over 1 percent between 1988 and 1994.

Rising rates of both obesity and high blood pressure appeared to account for most of the increase, said Dr. Hyon K. Choi, a professor of medicine at Boston University School of Medicine and the senior researcher on the study.

The high prevalence of gout in recent years is not surprising, Choi told Reuters Health.

"It had been on the rise before," he said, "and there was no reason to believe that it would be slowing down, since risk factors are on the rise."

Choi has served as an advisor to Takeda Pharmaceuticals, which also funded the study.

Takeda makes the gout medication Uloric and had obtained the North American marketing rights for the diet pill Contrave, which was rejected by U.S. regulators earlier this year.

Gout is a very painful form of arthritis that causes the joints to periodically become swollen, red and hot -- most often affecting the big toe, though it also strikes the feet, ankles, knees, hands and wrists.

The condition arises when uric acid crystals build up in the joints. The body produces uric acid when it breaks down purines -- substances found naturally in the body, and in high concentrations in foods like organ meats, anchovies, mushrooms and some seafood, such as herring and mackerel.

Factors that boost the body's production of uric acid, or slow the removal of it, also raise the risk of gout. Besides obesity and high blood pressure, those factors include diabetes, taking certain medications -- like blood pressure drugs called thiazide diuretics -- and heavy drinking.

The current findings, reported in the journal Arthritis & Rheumatism, are based on data from a periodic federal health survey of U.S. adults.

Choi's team compared the 2007-2008 survey, which included 5,700 adults, with surveys done between 1988 and 1994, which involved nearly 19,000 men and women.

In the latest survey, about 4 percent of respondents said a doctor had diagnosed them with gout. That was true of only 1.2 percent of respondents in the earlier surveys.

Those numbers were backed up by objective tests as well. In the most recent study, more than 21 percent of men and women had high uric acid levels, versus only 3 percent in the 1988-94 surveys.

When Choi's team factored in obesity and high blood pressure rates, they appeared to account for the rising gout prevalence.

For the average American, he said, the findings underscore the importance of the lifestyle measures we should be taking anyway. That includes limiting red meat, drinking only in moderation, getting regular exercise and eating a well-balanced diet -- rich in fruits, vegetables, whole grains and unsaturated fats.

"That will help with not only gout," Choi noted, "but other conditions like diabetes and heart disease."